Contrasted histories of organelle and nuclear genomes underlying physiological diversification in a grass species

C₄ photosynthesis evolved multiple times independently in angiosperms, but most origins are relatively old so that the early events linked to photosynthetic diversification are blurred. The grass Alloteropsis semialata is an exception, as this species encompasses C₄ and non-C₄ populations. Using phylogenomics and population genomics, we infer the history of dispersal and secondary gene flow before, during and after photosynthetic divergence in A. semialata. We further analyse the genome composition of individuals with varied ploidy levels to establish the origins of polyploids in this species. Detailed organelle phylogenies indicate limited seed dispersal within the mountainous region of origin and the emergence of a C₄ lineage after dispersal to warmer areas of lower elevation. Nuclear genome analyses highlight repeated secondary gene flow. In particular, the nuclear genome associated with the C₄ phenotype was swept into a distantly related maternal lineage probably via unidirectional pollen flow. Multiple intraspecific allopolyploidy events mediated additional secondary genetic exchanges between photosynthetic types. Overall, our results show that limited dispersal and isolation allowed lineage divergence, with photosynthetic innovation happening after migration to new environments, and pollen-mediated gene flow led to the rapid spread of the derived C₄ physiology away from its region of origin.     

Strong divergent selection at multiple loci in two closely related species of ragworts adapted to high and low elevations on Mount Etna

Recently diverged species present particularly informative systems for studying speciation and maintenance of genetic divergence in the face of gene flow. We investigated speciation in two closely related Senecio species, S. aethnensis and S. chrysanthemifolius, which grow at high and low elevations, respectively, on Mount Etna, Sicily and form a hybrid zone at intermediate elevations. We used a newly generated genome‐wide single nucleotide polymorphism (SNP) dataset from 192 individuals collected over 18 localities along an elevational gradient to reconstruct the likely history of speciation, identify highly differentiated SNPs, and estimate the strength of divergent selection. We found that speciation in this system involved heterogeneous and bidirectional gene flow along the genome, and species experienced marked population size changes in the past. Furthermore, we identified highly‐differentiated SNPs between the species, some of which are located in genes potentially involved in ecological differences between species (such as photosynthesis and UV response). We analysed the shape of these SNPs’ allele frequency clines along the elevational gradient. These clines show significantly variable coincidence and concordance, indicative of the presence of multifarious selective forces. Selection against hybrids is estimated to be very strong (0.16–0.78) and one of the highest reported in literature. The combination of strong cumulative selection across the genome and previously identified intrinsic incompatibilities probably work together to maintain the genetic and phenotypic differentiation between these species – pointing to the importance of considering both intrinsic and extrinsic factors when studying divergence and speciation.     

Moths in fragments: insights into the biology and ecology of the Australian endangered golden sun moth Synemon plana (Lepidoptera: Castniidae) in natural temperate and exotic grassland remnants

The conservation and management of endangered species requires an adequate understanding of their biology and ecology. Although there has been an increasing appreciation in Australia of the need for greater efforts to conserve insects, there is only limited information available that can be used to underpin conservation efforts. The endangered golden sun moth, Synemon plana (Lepidoptera: Castniidae) is a flagship species endemic to natural temperate grassland in south-eastern Australia. Most populations of this species are at considerable risk from habitat loss, weed invasion and inadequate management. Despite the considerable knowledge that exists about the species biology and ecology, efforts to improve the species conservation status are hampered because there are still critical gaps in our understanding of the species’ natural history. In particular, the ecology of the larvae is not known. Our study examined the abundance, population structure and reproductive biology of the moths in a broad sample of both natural temperate and exotic grassland remnants in and near Canberra in the Australian Capital Territory (ACT) in south-eastern Australia. The results fill critical gaps in the knowledge needed to achieve effective conservation management. From our findings, it is clear that the species inhabits grasslands dominated by a mixture of native wallaby grasses (Rytidosperma spp. (formerly Austrodanthonia)) and spear grasses (Austrostipa spp.). In contrast to earlier suggestions that S. plana is entirely confined to natural temperate grassland, mature and immature life stages of the species were also present in grasslands comprised entirely of the exotic Chilean needlegrass (Nassella neesiana). Most of the S. plana populations surveyed in the ACT were characterised by low relative abundance with only very few large populations being recorded. The conservation of exotic grasslands as substitute habitat for S. plana is discussed and suggestions regarding future monitoring and research of the species are provided.     

Simulating the effects of climate change on the distribution of an invasive plant,using a high resolution,local scale,mechanistic approach: challenges and insights

The growing economic and ecological damage associated with biological invasions, which will likely be exacerbated by climate change, necessitates improved projections of invasive spread. Generally, potential changes in species distribution are investigated using climate envelope models; however, the reliability of such models has been questioned and they are not suitable for use at local scales. At this scale, mechanistic models are more appropriate. This paper discusses some key requirements for mechanistic models and utilises a newly developed model (PSS[gt]) that incorporates the influence of habitat type and related features (e.g., roads and rivers), as well as demographic processes and propagule dispersal dynamics, to model climate induced changes in the distribution of an invasive plant (Gunnera tinctoria) at a local scale. A new methodology is introduced, dynamic baseline benchmarking, which distinguishes climate‐induced alterations in species distributions from other potential drivers of change. Using this approach, it was concluded that climate change, based on IPCC and C4i projections, has the potential to increase the spread‐rate and intensity of G. tinctoria invasions. Increases in the number of individuals were primarily due to intensification of invasion in areas already invaded or in areas projected to be invaded in the dynamic baseline scenario. Temperature had the largest influence on changes in plant distributions. Water availability also had a large influence and introduced the most uncertainty in the projections. Additionally, due to the difficulties of parameterising models such as this, the process has been streamlined by utilising methods for estimating unknown variables and selecting only essential parameters.     

Introduced populations as genetic reservoirs for imperiled species: a case study of the Arkansas River Shiner (Notropis girardi)

The Arkansas River Shiner is a threatened species that has been extirpated throughout much of its native range (Arkansas River drainage) and remaining populations are imperiled. Prior to 1978, this species was accidently introduced to the Pecos River (Rio Grande drainage) via bait bucket, and has since persisted for over 30 years. Genetic data show that the Pecos River population maintains comparable levels of diversity at mitochondrial DNA and microsatellite loci relative to native range populations. Hence, we examined several factors that could be responsible for high introduced genetic diversity including (a) multiple introductions from genetically distinct sources (b) introduction of individuals from a genetically diverse source followed by rapid population expansion, (c) presence of life-history traits that foster propagule diversity and wide spatio-temporal demographic and genetic mixing; and (d) introduction to a suitable habitat in the non-native range. Our findings indicate Arkansas River Shiner was likely introduced from the Canadian River and subsequently experienced rapid population expansion that mitigated loss of diversity during the founding event. Threats to native Arkansas River Shiner have increased due to ongoing drought and water resource development, thus a finding of high diversity in the Pecos River suggests conservation significance of this non-native population. Further, it identifies the Pecos River as both a refuge for native endemic fishes and of genetic diversity of introduced, yet threatened, species.     

The interplay between tissue growth and scaffold degradation in engineered tissue constructs

In vitro tissue engineering is emerging as a potential tool to meet the high demand for replacement tissue, caused by the increased incidence of tissue degeneration and damage. A key challenge in this field is ensuring that the mechanical properties of the engineered tissue are appropriate for the in vivo environment. Achieving this goal will require detailed understanding of the interplay between cell proliferation, extracellular matrix (ECM) deposition and scaffold degradation. In this paper, we use a mathematical model (based upon a multiphase continuum framework) to investigate the interplay between tissue growth and scaffold degradation during tissue construct evolution in vitro. Our model accommodates a cell population and culture medium, modelled as viscous fluids, together with a porous scaffold and ECM deposited by the cells, represented as rigid porous materials. We focus on tissue growth within a perfusion bioreactor system, and investigate how the predicted tissue composition is altered under the influence of (1) differential interactions between cells and the supporting scaffold and their associated ECM, (2) scaffold degradation, and (3) mechanotransduction-regulated cell proliferation and ECM deposition. Numerical simulation of the model equations reveals that scaffold heterogeneity typical of that obtained from $\mu $ CT scans of tissue engineering scaffolds can lead to significant variation in the flow-induced mechanical stimuli experienced by cells seeded in the scaffold. This leads to strong heterogeneity in the deposition of ECM. Furthermore, preferential adherence of cells to the ECM in favour of the artificial scaffold appears to have no significant influence on the eventual construct composition; adherence of cells to these supporting structures does, however, lead to cell and ECM distributions which mimic and exaggerate the heterogeneity of the underlying scaffold. Such phenomena have important ramifications for the mechanical integrity of engineered tissue constructs and their suitability for implantation in vivo.     

Two silicone nontoxic fouling release coatings: Hydrosilation cured PDMS and CaCO3 filled,ethoxysiloxane cured RTV11

Two silicone coatings have been evaluated for barnacle adhesion. One coating is an unfilled hydrosilation cured polydimethylsiloxane (PDMS) network, while the other is a room temperature vulcanized (RTV), filled, ethoxysiloxane cured PDMS elastomer, RTV11^?. The adhesion strength of one species of barnacle, Balanus eburneus, to the hydrosilation coatings is in the range of 0.37–0.60 kg cm^‐2 while the corresponding range for RTV11 is 0.64–0.90 kg cm^‐2. The easier release of B. eburneus from the hydrosilation cured network compared to RTV11 is discussed in relationship to differences in bulk and surface properties. Preliminary results suggest bulk modulus may be the most important parameter in determining barnacle adhesion strength. In light or mechanical property analysis, a re‐evaluation of surface properties and chemical stability is presented.     

Substituted imidazopyridazines are potent and selective inhibitors of Plasmodium falciparum calcium-dependent protein kinase 1 (PfCDPK1)

A series of imidazopyridazines which are potent inhibitors of Plasmodium falciparum calcium-dependent protein kinase 1 (PfCDPK1) was identified from a high-throughput screen against the isolated enzyme. Subsequent exploration of the SAR and optimisation has yielded leading members which show promising in vitro anti-parasite activity along with good in vitro ADME and selectivity against human kinases. Initial in vivo testing has revealed good oral bioavailability in a mouse PK study and modest in vivo efficacy in a Plasmodium berghei mouse model of malaria.     

How many conservation units are there for the endangered grassland earless dragons?

Species are the most commonly recognised unit for conservation management, yet significant variation can exist below the level of taxonomic recognition and there is a lack of consensus around how a species might be defined. This definition has particular relevance when species designations are used to apportion conservation effort and when definitions might be made through legislation. Here, we use microsatellite DNA analyses to test the proposition that the last remaining populations of the endangered grassland earless dragon (Tympanocryptis pinguicolla) harbour substantial cryptic genetic variation. Our study provides strong evidence that long historical isolation and the recent impacts of urbanization, have led to genetic differentiation in microsatellite DNA allele frequencies and high numbers of private alleles among three genetic clusters. This differentiation is partially concordant with previous mitochondrial DNA analyses, which show the two regions (Canberra and Monaro) where this species exists, to be reciprocally monophyletic, but differs through the identification of a third genetic cluster that splits a northern Canberra cluster from that of southern Canberra. Our data also identify a stark contrast in population genetic structure between clusters such that high levels of genetic structure are evident in the highly urbanised Canberra region but not in the largely rural Monaro region. We conclude that this species, like many reptiles, harbours considerable cryptic variation and currently comprises three distinct and discrete units. These units could be classified as separate species for the purpose of conservation under the relevant Australian and international Acts drawing management appropriate to that status.